1. Field
This disclosure relates generally to semiconductor memory devices, and more specifically, to conductive bridge random access memory devices and methods of making the same.
2. Related Art
Programmable metallization memories, also referred to as conductive bridge random access memory (CBRAM) cells, generally consist of a chalcogenide material/silver diffusion layer that is sandwiched between a bottom electrode (e.g. W) and an upper electrode (Ag or Cu). Memory cell operation is believed to be due to formation/dissolution of a conductive bridge formed by electro-deposition of silver. It is important to have diffusion of silver ions to chalcogenide occur in a controllable manner. However, in the current known fabrication method for CBRAM cells, silver is deposited by a physical vapor deposition (PVD) process. In such a method, silver diffuses rapidly into the chalcogenide during the PVD step itself and thus the silver diffusion is largely uncontrolled. This results in significant variability in the memory cell operation from one cell to another. In addition, removal of sputter deposited silver from unwanted areas is also a difficult process.
Accordingly, there is a need for an improved method and apparatus for overcoming the problems in the art as discussed above.